The data traffic of mobile communication has steeply increased due to the rapid popularization of smartphones, tablet terminals and the like in recent years. Therefore, it was internationally agreed at the World Radio Conference held in 2007 (WRC-07) that a band of 3.5 GHz or the like should be secured as a frequency band for 4 G (Generation) such as LTE (Long Term Evolution)-Advanced. It is expected that in the future, in order to deal with the steep increase of traffic, such new frequency bands will be allocated for the 4 G. In addition, as solutions to deal with increased traffic in the entire system, a heterogeneous network configuration has been examined in which a plurality of small cell base stations is installed in the area of a general macrocell base station, high-density installation of small cell base stations, and the like.
Traffic at each radio base station fluctuates per unit time depending on the location where each radio base station is installed. For example, peak data traffic is reached in an office area during daytime which is a working time zone whereas peak data traffic is reached in a residential area during the evening after individuals return home from work or school. In both the areas, the traffic decreases at midnight. In the current system, radio communication process resources are implemented based on the peak traffic of each area for each base station, and the process resources of all the base stations remain operating when the traffic is reduced.
In recent years, to prepare for the time in the future when there will be a high-density installation of small cell base stations that correspond to the steep traffic increase, an architecture has been proposed that is referred to as C-RAN for collecting, in one base station apparatus, radio communication processing units for baseband signal processing or the like of a plurality of base stations. The concept of the C-RAN architecture is based on a technology that enables low cost and low power consumption to be achieved at the base station apparatus by efficiently sharing the process resources of the collected radio communication processing units among the plurality of base stations. In other words, since the radio communication processes are collected in one base station apparatus, and since ideally the traffic of all the areas can be dealt with in an average form by implementing the process resources based upon peak mobile data traffic, a small apparatus size and low cost can be achieved. In addition, this technology enables the number of process resources that operatd during low traffic to be dramatically reduced by resource sharing, thus achieving low power consumption.
Here, the efficient achievement of the C-RAN architecture necessitates an arithmetic scheduling (resource allocation control) technology for reducing the number of baseband cards or the number of computing units to be operated as much as possible by sharing the computing units collected according to the fluctuation of communication traffic of each base station. As arithmetic scheduling technology (arithmetic resource allocation technology) for the base station apparatus, several technologies have been disclosed (e.g., refer to PTL. 1 to 3).
PTL. 1 discloses a technology for preventing a call loss by efficiently allocating resources at a base station having a card for performing a plurality of baseband signal processes under traffic changed with time. According to this technology, resource monitoring means, resource control means, and traffic recording means are provided, and process resource reallocation is started when the number of available resources is lower than a threshold value. Further, the threshold value is changed on the basis of the most frequently generated call at each time zone. In other words, unnecessary process resource reallocation is prevented by changing the threshold value on the basis of the number of resources that are used for the most frequently generated call.
PTL. 2 discloses a technology for controlling the number of baseband cards in an operated state at a radio base station apparatus. This radio base station apparatus is a base station apparatus that includes a plurality of baseband cards, a measurement unit configured to measure the amount of each resource that is used, and a control unit configured to perform resource reception switching of each baseband card on the amount of the resource that is used. At this radio base station apparatus, the reception switching is carried out in consideration of a card capable of receiving both an existing service and a service to which a HSDPA (High-Speed Downlink Packet Access) method or a HSUPA (High-Speed Uplink Packet Access) method is applied (hereinafter, referred to as HS service) and a card incapable of receiving the HS service.
PTL. 3 discloses a technology for switching the connection state of a plurality of radio resources in a radio communication system that uses an OFDMA (Orthogonal Frequency Division Multiple Access) method. This technology is characterized in that a frequency bandwidth allocated to each sector is changed corresponding to the number of terminals, and a base station apparatus includes radio resource allocation means for each sector and resource connection state switching means corresponding thereto.